Born Overseas: How to Find Your Correct BaZi Hour (Time Zones & True Solar Time)

The Short Answer: Use the Birthplace’s True Solar Time — Never Beijing Time

Many overseas Chinese parents’ first instinct is to “convert the birth time to Beijing time before charting” — this is the single most common mistake. The BaZi and Qi Men double-hour fundamentally describes the sun’s position relative to the place of birth: when the sun is highest overhead, it is the middle of the Wu hour, wherever you are. A child born in Los Angeles is charted by the sun over Los Angeles; Beijing’s clocks are irrelevant.

The correct reference is the True Solar Time of the birthplace (what is True Solar Time?), reached in three steps.

The Three-Step Conversion

Step 1: Take the Local Time from the Birth Certificate

Overseas birth certificates record local legal time. Use it as-is — do not convert across time zones.

Step 2: Undo Daylight Saving Time (DST)

Most of North America, Europe and Australia observe DST, during which clocks run one hour ahead. If the birth fell within DST, subtract one hour to recover standard time. DST rules vary by region and by decade (the current US rule runs from the second Sunday of March to the first Sunday of November) — for older birth dates, check the rule in force that year.

Step 3: Longitude Correction + Equation of Time

Longitude difference: every degree between the birthplace and its time zone’s reference meridian shifts solar time by 4 minutes (east adds, west subtracts);
Equation of Time: the seasonal deviation caused by Earth’s elliptical orbit, ranging from −14 to +16 minutes through the year.

Worked Example: A Child Born in Los Angeles

Suppose a child was born in Los Angeles on July 15, 2010 at 2:30 PM:

July is Pacific Daylight Time (PDT); subtract one hour → 1:30 PM standard time (PST);
Los Angeles sits at about 118.24°W; the PST reference meridian is 120°W, a difference of +1.76° → add about 7 minutes;
The Equation of Time in mid-July is about −6 minutes;
True Solar Time ≈ 1:30 PM + 7 − 6 = 1:31 PM → the Wei hour.

Here the raw clock time happens to give the same Wei hour — but a birth at 3:05 PM would read as the Shen hour on the clock while its true solar time is still Wei. Near an hour boundary, correction changes the entire chart.

The Twelve Double-Hours (by True Solar Time)

Hour	True Solar Time	Hour	True Solar Time
Zi 子	23:00–01:00	Wu 午	11:00–13:00
Chou 丑	01:00–03:00	Wei 未	13:00–15:00
Yin 寅	03:00–05:00	Shen 申	15:00–17:00
Mao 卯	05:00–07:00	You 酉	17:00–19:00
Chen 辰	07:00–09:00	Xu 戌	19:00–21:00
Si 巳	09:00–11:00	Hai 亥	21:00–23:00

Note: births after 23:00 raise the “late Zi hour” question of which day the day pillar belongs to. Schools differ; the mainstream convention starts the next day’s Zi hour.

Let a Tool Do the Math

The manual three-step conversion is easy to get wrong on DST rules and the Equation of Time. The Qimena AI charting tool natively supports negative (western) longitudes and GPS auto-detection: enter the birthplace longitude (e.g. −118.24 for Los Angeles) and every correction is applied automatically before the chart is cast. New York, Los Angeles, London and Sydney are built into the city presets.